Patent GB-836871-A (GB)
Title: Velocity modulation electron tube apparatus
IPC: H01J25/12
Filed: 1956-06-12
Abstract: 836,871. Velocity modulated tubes. VARIAN ASSOCIATES. June 12, 1956 [June 14, 1955], No. 18170/56. Class 39(1). A klystron has a resonator tuned by a plunger 57, Fig. 7, guide means 63, 64 maintaining the alignment of the plunger in the resonator, a rack 62 coupled to the plunger and a pinion 65, 66 meshing with the rack 62 and effecting translational movement of the plunger 57. The plunger is partly supported by a flexible diaphragm 58 of copper plated " Monel " (Registered Trade Mark) which is rectangular and secured to the resonator wall by two opposed edges, the other two edges being spaced slightly from the resonator wall and the plunger stem is sealed vacuum tightly to cup 61 by bellows 59. The toothed bar tuning rack 62 is 90 degrees spaced from two support guides 63 which are smooth bars of rectangular cross-section which slide in rectangular "Teflon" (Registered Trade Mark) lined recesses in block 64. The pinion which is held in a mount through which it passes and its supporting rod 66 is actuated preferably from a remote station by worm shaft 73 via toothed worm gearing 69. The gun structure has a take apart envelope joint 12, Fig. 4, having cylindrical and flat abutting spacing and aligning surfaces separated by a gap too large for capillary forces to operate, otherwise capillary forces would cause the sealing adhesive 25 to flow to the cylindrical abutting surfaces so destroying the vacuum tightness of the seal. The cathode may be replaced by removing the adhesive and opening the joint. The indirectly heated cathode 35 has a concave emitting surface and is secured to focusing electrode 36 by a ring 37 with heat reflecting fingers which grip the cathode at their free ends as described in Specification 836,873. Some of the fingers can be omitted to facilitate evacuation. In a modification certain fingers are bent outwardly to constant diameter, the cathode being secured to the inwardly convergent fingers. The cathode heater is a double spiral, and a double partition heat shield 42 is provided. The cathode has a concave emitting surface which co-operates with the focusing electrode 36 to produce an initially convergent beam, the cathode being magnetically shielded by steel envelope portions 13, 14 and the beam passing through a tunnel in magnetic iron polepiece 24 into the main focusing field of coils 11, Fig. 1, a second iron polepiece 54 being provided at the collector end of the tube. The heater leads 44, 45 are supported from metal envelope portions and terminals 23, 18, 44 are supported via disc 49 and the central heater support 46 which does not carry current (because of insulator 47) is secured to envolpe portion 21 via getter flange 51. The metal parts are sealed together by glass collars 16, 19, 22. The cathode-focusing electrode has concentric external terminals, Fig. 1A (not shown), which engage spring contacts on a socket as the cathode end of the tube is inserted in its oil bath. The collector Fig. 7 is closed by cone 95 and has a helical channel 94, 97 for circulation of water which enters and leaves via ring passage 99 and conical passage 95-98 respectively. A vacuum pump is attached to output wave guide 8 which has iris 74, and further iris 76 to block secondaries emitted by the drift tube 52. A step 92 ensures that the tube is correctly centred and aligned in the focusing coils. The waveguide window, Fig. 10, is clamped between two guide sections by means of rectangular flanges 81, 82 and gasket 87 of "neoprene" associated with a resilient pad of conducting wire mesh 85 which are drawn together by four bolts 80. A further " neoprene " gasket provided to secure polepiece 24 to support 91. The wave guide can be pressurized on the output side of the window to avoid flashovers. The tube shown in a cascade amplifier, the drift tubes having cooling coils 53, Fig. 1. Stiffener plates 55 and stiffener rods 56 reduce microphony are provided as described in Specification 836,872 and are made of non-magnetic stainless steel so as not to disturb the magnetic focusing field. The tube is a high frequency high gain pulse amplifier operating at high power and is used in radar, navigation beacons and a linear accelerators.